The Space Launch System uses two solid rocket boosters that provide most of the thrust during launch. Each booster contains propellant made of ammonium perchlorate, aluminum, and binders that ignite and burn for 124 seconds. The boosters are jettisoned at an altitude of 45 km after which parachutes deploy to slow their descent into the ocean for recovery. A range safety system can destroy the boosters by remote command if needed for safety.

1. GOKUL LAKSHMANAN
M.TEC H TH ER MA L A N D FLU ID EN GIN EER IN G
NASA’S SPACE LAUNCH SYSTEM:
AHEAVY-LIFT PLATFORM FOR ENTIRELY NEW
MISSIONS

2. Contents
 Solid Rocket Booster (SRB)
 SRB testing
 Components
 Operation sequence
 Range safety system

3. Solid Rocket Booster (SRB)
 2 Solid fuel rocket boosters
used for primary
propulsion
 Provided the majority of
the thrust during the first
two minutes of flight.
 Thrust :16000 kN
 Burn time 124 seconds
 Fuel : Poly-butadiene
acrylonitrile, Ammonium
perchlorate composite
propellant

4.  Burns up to an altitude of about 45 km
 Non - reusable
 Material : Aluminum / Steel and composite materials
 Operation : Igniting, Steering and Jettison of the
boosters

6. SRB Testing

7. Components
1. Hold-down posts
 Each solid rocket booster has four hold-down posts
 Hold-down bolts hold the SRB and launcher
platform together
 Hold down nuts contains NASA Standard
Detonators(NSD) which were ignited at SRB ignition
commands
 NSD ignite and splits the nut into two or more parts
 Hold-down bolt travels downward
 Bolt were stopped by the stud deceleration stand
which contains sand
 The SRB bolt is 710 mm long and 89 mm in diameter

9. 2. Electrical power distribution
 DC power is distributed to each SRB via SRB buses
labeled A, B and C
 SLS main DC buses A, B and C supplies power to
corresponding SRB buses A, B and C.
 In addition, SLS main DC bus C supplied backup power
to SRB buses A and B, and SLS bus B supplied backup
power to SRB bus C.
 This electrical power distribution arrangement allowed
all SRB buses to remain powered in the event one SLS
main bus failed
 The nominal operating voltage was 28±4 volts DC.

11. 3. Hydraulic power units
 Two self-contained, independent Hydraulic Power
Units (HPUs) on each SRB
 HPU consisted of an auxiliary power unit, hydraulic
pump, hydraulic reservoir and hydraulic fluid
manifold
 The APUs were fueled by hydrazine
 Generates mechanical shaft power to drive a
hydraulic pump that produced hydraulic pressure for
the SRB hydraulic system.

12.  Hydrazine is feed into a gas generator. The gas
generator decompose the hydrazine into hot, high-
pressure gas
 A turbine converted this into mechanical power,
driving a gearbox.
 The gearbox drive the fuel pump, its own lubrication
pump, and the HPU hydraulic pump.
 The waste gas from gas generator now cooler and at
low pressure, was passed back over the gas generator
housing to cool it before being dumped overboard.

13.  Each HPU is connected to servo actuators
 The hydraulic pump speed was 3600 rpm and
supplied hydraulic pressure of 21.03 ± 0.34 Mpa
 Hydraulic pressure is used to drive Thrust vector
controller
 The hydraulic system is operated from T minus 28
seconds until SRB separation from the SLS

15. 4. Thrust vector control
 Each SRB had two hydraulic servo actuators, to
move the nozzle up/down and side-to-side.
 This provided thrust vectoring to help control the
vehicle in all three axes (roll, pitch, and yaw).
 Each SRB servo actuator consist of four independent,
servo valves that receive signals from the drivers.
 Each servo valve control one actuator ram and thus
nozzle to control the direction of thrust.

17. 5. Propellant
Component Description % by weight
Ammonium
Perchlorate
oxidizer 69.6% by weight
Aluminum fuel 16%
Iron oxide a catalyst 0.4%
Poly butadiene
acrylonitrile
Serves as a binder that hold the
mixture together and acted as
secondary fuel
12.04%

18. OPERATION SEQUENCE
1. Ignition
 Ignition can occur only when a manual lock pin from
each SRB has been removed.
 The ground crew removes the pin during prelaunch
activities at T minus five minutes
 The solid rocket booster ignition commands are
issued when four cryogenic engines are at or above
90% rated thrust
 The solid rocket ignition commands were sent by the
on-board computers

19.  The fire commands
cause the NSDs on the
SRB to fire.
 This ignites a pyro
booster charge.
 The booster charge
ignites the propellant in
the SRB which fires down
the entire vertical length

20.  This ignites the solid
rocket propellant along
its entire surface area
instantaneously.
 At t minus zero, the two
SRBs are ignited, under
command of the four
onboard computers

21.  Separation of the four
explosive bolts on each SRB
is initiated
 The two umbilical cords are
retracted
 The onboard master timing
unit and event timer are
started
 The four cryogenic engines
are at 100% and the ground
launch sequence is
terminated and liftoff occurs

22. 2. Separation
 The SRBs are jettisoned from SLS at altitude, about
45 km.
 SRB separation is initiated when chamber pressure
of both SRBs is less than or equal to 340 kPa.
 The SRBs separate from the SLS within 30
milliseconds of the firing command.

23.  The forward attachment point consists a nut-bolt
system. It contains one NSD pressure cartridge.
 The aft attachment points consist of three separate
struts: upper, diagonal and lower. Each strut
contains one bolt with an NSD pressure cartridge at
each end.
 Detonating the NSD via electrical system separates
the SRB’s

24. 3. Descent and Recovery
 The SRBs are jettisoned
from the SLS at 2 minutes
and an altitude of about 45
km.
 After continuing to rise to
about 67 km the SRBs begin
to fall back to earth
 Once back in the
atmosphere are slowed by a
parachute system to prevent
damage on ocean impact

25.  Nose cap separation occurs at a nominal altitude of
5km, about 218 seconds after SRB separation.
 This triggers the parachute to open and SRB falls to
ocean
 A command is sent from the SNS to the SRB just
before separation to apply battery power to the
recovery logic network
 SRB is recovered by US Navy

26. SRB Flash Down into Ocean

27. Range safety system
 A range safety system provides destruction of rocket or
its parts with on-board explosives by remote command if
the rocket is out of control
 This limits the danger to people on the ground from
crashing pieces, explosions, fire, poisonous substances,
etc.
 Two RSSs one in each SRB.
 Capable of receiving command messages transmitted
from the ground station.
 The RSS was used only when the shuttle vehicle violates
launch trajectory

28.  Two confined detonating fuse manifolds (CDF)
 The NSDs provide the spark to ignite the CDF which
results in booster destruction.
 The safe and arm device provides mechanical
isolation between the NSDs and the CDF before
launch and during the SRB separation sequence.